The goal of this project is to gain new information about the molecular nature of intercellular recognition and adhesion in early mammalian embryogenesis. Since it would be very difficult to obtain enough normal embryonic material for the biochemical studies proposed, we plan to use teratocarcinoma stem cells, which are closely similar to normal pluripotent embryonic cells, as a source of material. Our working hypothesis is that intercellular recognition and adhesion during early mammalian development is mediated by the interaction of a cell surface carbohydrate-binding component on one cell with its complementary carbohydrate-containing receptor on an adjacent cell. We have identified a carbohydrate-binding component with fucan/mannan specificity on the surface of teratocarcinoma stem cells. We have also identified a hemagglutinin (lectin) with almost identical specificity present in soluble stem cell extracts. We have purified the lectin, a 56,000 MW protein, and are in the process of raising antibody to it. The antibody will be used to study the tissue distribution of the lectin during the teratocarcinoma stem cell differentiation in vitro and during the development of early mouse embryos. We have also determined that stem cell adhesion has divalent cation-independent and -dependent components and that the lectin is involved in divalent cation independent adhesion. We also propose to identify the endogenous cell surface carbohydrate-containing receptor for the lectin.